I have the additional 40L tank fitted above the spare and I am not sure how this affects the electronic fuel consumption calculations. I get the feeling it shows the car as being heavier on petrol than I suspect from doing the old fill it up and see how much mileage you get. It definitely is not ignoring the extra 40L of fuel on board. At the same time I know that the odometer may well be out when compared to GPS. Anyone else have the extra tank who is doubting the numbers?

It came down to the resetting of the electronic calculations will only happen when there is a fuel increase greater than "x". You have a normal overflow long range tank, which means that for the first 40 litres you use from the main tank, the tank will stay full, BUT, the calculation is done once off (i.e. when you fill up). Thereafter it just counts down, it will not reset unless it is topped up (when you have emptied the 40l aux tank) with "x" amount of fuel. not sure what the "x" amount is though.

I also have a 40l auxiliary tank between the chassis and spare that feeds into the main tank and I have not noticed any difference in the Consumption display. It's still morreless the same as what it used to be, and under certain conditions it changes as I would expect it to change.

What Dewald is referring to is the Range readout. I found that if I park the Hilux nose up on an incline for about 10 minutes, to drain some fuel into the aux tank, and then park it level again, the float would have moved enough to reset the Range display.

ThysdJ wrote:I also have a 40l auxiliary tank between the chassis and spare that feeds into the main tank and I have not noticed any difference in the Consumption display. It's still morreless the same as what it used to be, and under certain conditions it changes as I would expect it to change.

What Dewald is referring to is the Range readout. I found that if I park the Hilux nose up on an incline for about 10 minutes, to drain some fuel into the aux tank, and then park it level again, the float would have moved enough to reset the Range display.

Ah range readout....now it makes sense. I guess my odometer must be a bit out then

Thanks Thys....one last thing that has been bugging me is the link between speedometer and odometer....if speedo reads say 10% over is it then the case that the odometer also reads 10% over? I don't know to what extent they are connected.

That is partially correct, the 10% over is not through the entire spectrum of speedometer readings, there will probably be an average of the average speed (let's say 6%), thus your odometer will be "out" with 6% in the long run.

That is partially correct, the 10% over is not through the entire spectrum of speedometer readings, there will probably be an average of the average speed (let's say 6%), thus your odometer will be "out" with 6% in the long run.

Some interesting observations...so at 100 km/h on speedo the GPS reads only 93 km/h so as expected the speedo is a bit optimistic.

But....the odometer is actually very accurate. The GPS distance reading is 99% of odometer reading with stock standard 265/70x16 tyres. So the fuel consumption reading is way worse than the actual fuel consumption. That is good to know and I can now ignore the thing and do the calc the way we always did.

Interesting that most people say that going to 265/75x16 makes the speedo more accurate, but then the odometer will seriously under-read.